• Pil-Jae Kong, Hee Jae Lee, Sang-Hyun Lee, Su Young Kim, Su Nam Lee, Wan-Joo Chun, and Sung-Soo Kim.
• Department of Pharmacology, College of Medicine, Kangwon National University, 192-1 Hyoja 2-Dong, Chunchon, Kangwon-Do 200-701, Republic of Korea.
• Neurosci. Lett. 2008 Mar 15; 433 (3): 215-8.

AbstractDouble-stranded RNA (dsRNA) has been implicated as a potential immune stimulant in activating microglia, which can cause chronic neurodegeneration. In this study, we examined the involvement of different types of mitogen-activated protein kinases (MAPKs) in the induction of inducible nitric oxide synthase (iNOS) by dsRNA in microglial cells. Nitric oxide production was increased after exposure of microglia to 50mug/mL dsRNA. Levels of dsRNA-induced nitrite production in a line of immortalized murine microglia (BV2) and in primary cultures of murine microglia were decreased by inhibition of JNK or p38 MAPK, but were increased by inhibition of extracellular signal-regulated kinase. Similar results were shown in the levels of dsRNA-induced iNOS gene expression in BV2 cells. Phosphorylation levels of p38 MAPK were increased, depending on p38 MAPK inhibitor concentrations, while activation levels of MAPKAPK2, a known p38 substrate, were inhibited. Thus, it is likely that SB203580 inhibited the kinase activity of p38 MAPK, resulting in the loss of a feedback inhibition regulatory loop of p38 MAPK in BV2 cells. These findings suggest that dsRNA stimulated iNOS expression via MAPK signaling pathways, including JNK and p38 MAPK.

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